Nicolas Javahiraly

A reliable, sensitive and fast optical fiber hydrogen sensor based on surface plasmon resonance.

We report for the first time on the experimental response of a Surface Plasmon Resonance fiber optic sensor based on wavelength modulation for hydrogen sensing. This approach of measuring the hydrogen concentration makes the sensor insensitive to intensity fluctuations. The intrinsic fiber sensor developed provides remote sensing and enables the possibility of multi-points sensing. The sensor consists of a multilayer of 35 nm Au/180 nm SiO2/Pd deposited on a step- index multimode fiber core. The sensitivity and selectivity of the sensor are optimal at a Pd thickness of 3.75 nm. The sensor is sensitive to a hydrogen concentration ranging between 0.5 and 4% H2 in Ar, with a response time less than 15 s.

Wavelength response of a surface plasmon resonance palladium-coated optical fiber sensor for hydrogen detection

An optical fiber using palladium as sensitive layer is characterized in the range of 450 to 900 nm. The sensitive layer is deposited on the outside of a multimode fiber, after removing the optical cladding. The sensor is based on a measurement technique that uses the surface plasmon resonance effect. A continuous change in output intensity is observed as a function of the hydrogen concentration between 0.5% and 4% H2 by volume in Argon. The response shows that the transmitted intensity can either decrease or increase, depending on the selected wavelength. This behavior is directly related to the change in reflectance upon hydrogenation between the polarization s and p. The loading time is 30 s and the unloading time is 90 s in a mix of argon and 10% of oxygen. The detectors show a good reproducibility.

Review on hydrogen leak detection: comparison between fiber optic sensors based on different designs with palladium

Abstract. A review of optical fiber hydrogen sensors based on palladium (Pd) is presented. Palladium hydrogen optical fiber sensing systems can be considered as a model for other metal hybrid systems. In addition, the Pd hydrogen systems are well characterized in bulk, cluster, or thin film form. We focus on the fiber principles. We then discuss their performances regarding their configurations. We will conclude by introducing the challenges in designing an ideal hydrogen optical fiber sensor based on a metal hybrids approach and which design direction is considered the best to take.

Origin and Control of Sinusoidal Nonlinearities in Wavelength-Tuned Littman External Cavity Laser Diodes

In a recent paper, we presented the influence of sinusoidal nonlinearities in the wavelength sweeping speed on the performance of an absolute distance interferometry setup. Nonlinearities in an optical frequency modulation system are generally the source of degradation in performance. The interest of this study comes from the experimental observation of the good behavior of an absolute distance measurement system with the presence of sinusoidal nonlinearities in the wavelength sweeping speed obtained from an external cavity laser diode (ECLD). This paper presents experimental results obtained with a custom ECLD based on a Littman-Metcalf setup. We link the sinusoidal nonlinear sweep to some mechanical properties of the cavity. The main source of these nonlinearities comes from the digitization of the piezoelectric transducer excitation. Different types of excitation like super-Gaussian and ramp, including or not sinusoidal modulations, were implemented and analyzed. By this way, we are able to reduce the spectral width by a factor 3 without adding linearization electronics such as a servo-loop control on injection current or nonuniform samplers, and our system achieves a 3 times 10- 6 relative uncertainty on distance measurement with a number of samples reduced by a factor 8.

Hydrogen leak detection: a comparison between fiber optic sensors based on different designs

We present a review of optical fiber hydrogen sensors based on Palladium. Palladium hydrogen optical fiber sensing system can be considered as a model for other metal hybrid system. Besides, the Palladium hydrogen, systems are well characterized in bulk, cluster or thin film form. We focus on the fiber principles. We discuss then their performances regarding their configurations. We will conclude by introducing the challenges for designing an ideal hydrogen optical fiber sensor based on metal hybrids approach and which designing direction seen the best to take.

Spectral monitoring of toluene and ethanol in gasoline blends using Fourier-Transform Raman spectroscopy

The combination of fossil-derived fuels with ethanol and methanol has acquired relevance and attention in several countries in recent years. This trend is strongly affected by market prices, constant geopolitical events, new sustainability policies, new laws and regulations, etc. Besides bio-fuels these materials also include different additives as anti-shock agents and as octane enhancer. Some of the chemical compounds in these additives may have harmful properties for both environment and public health (besides the inherent properties, like volatility). We present detailed Raman spectral information from toluene (C7H8) and ethanol (C2H6O) contained in samples of ElO gasoline-ethanol blends. The spectral information has been extracted by using a robust, high resolution Fourier-Transform Raman spectrometer (FT-Raman) prototype. This spectral information has been also compared with Raman spectra from pure additives and with standard Raman lines in order to validate its accuracy in frequency. The spectral information is presented in the range of 0 cm-1 to 3500 cm-1 with a resolution of 1.66cm-1. This allows resolving tight adjacent Raman lines like the ones observed around 1003cm-1 and 1030cm-1 (characteristic lines of toluene). The Raman spectra obtained show a reduced frequency deviation when compared to standard Raman spectra from different calibration materials. The FT-Raman spectrometer prototype used for the analysis consist basically of a Michelson interferometer and a self-designed photon counter cooled down on a Peltier element arrangement. The light coupling is achieved with conventional62.5/125μm multi-mode fibers. This FT-Raman setup is able to extract high resolution and frequency precise Raman spectra from the additives in the fuels analyzed. The proposed prototype has no additional complex hardware components or costly software modules. The mechanical and thermal disturbances affecting the FT-Raman system are mathematically compensated by accurately extracting the optical path information of the Michelson interferometer. This is accomplished by generating an additional interference pattern with a λ = 632.8 nm Helium-Neon laser (HeNe laser). It enables the FT-Raman system to perform reliable and clean spectral measurements from the materials under observation.

Review of optical fiber sensor technologies for hydrogen leak detection in hydrogen energy storage

We introduce a review concerning hydrogen sensors already validated based on palladium, and we discuss the best ways to proceed to achieve an ideal hydrogen sensor. We discuss the performances regarding the configuration of an optical fiber hydrogen sensor as well as the used materials properties. We conclude that hydrogen sensors using plasmonic effects are a seductive way to follow.

Perform light and optic experiments in Augmented Reality

In many scientific studies lens experiments are part of the curriculum. The conducted experiments are meant to give the students a basic understanding for the laws of optics and its applications. Most of the experiments need special hardware like e.g. an optical bench, light sources, apertures and different lens types. Therefore it is not possible for the students to conduct any of the experiments outside of the university’s laboratory. Simple optical software simulators enabling the students to virtually perform lens experiments already exist, but are mostly desktop or web browser based. Augmented Reality (AR) is a special case of mediated and mixed reality concepts, where computers are used to add, subtract or modify one’s perception of reality. As a result of the success and widespread availability of handheld mobile devices, like e.g. tablet computers and smartphones, mobile augmented reality applications are easy to use. Augmented reality can be easily used to visualize a simulated optical bench. The students can interactively modify properties like e.g. lens type, lens curvature, lens diameter, lens refractive index and the positions of the instruments in space. Light rays can be visualized and promote an additional understanding of the laws of optics. An AR application like this is ideally suited to prepare the actual laboratory sessions and/or recap the teaching content. The authors will present their experience with handheld augmented reality applications and their possibilities for light and optic experiments without the needs for specialized optical hardware.

Study of a fiber optic sensor for hydrogen leak detection

We present a study of a fiber optic sensor for leak detection based on Surface Plasmon Resonance (SPR). We use Palladium as the sensitive material for hydrogen detection. In this configuration, the transducer layer is a multilayer stack made of a silver, a silica and Pd layer. The spectral modulation of the light transmitted by the fiber allows to detect hydrogen on the environment. The multilayer thickness defines the sensor performance. The silica thickness tunes the resonant wavelength whereas the silver and Pd thickness determines the sensor sensitivity. The study of the sensor performance as function of several thicknesses (Pd/Si/Ag) is achieved and we present the optimal configuration at a concentration of 4% hydrogen in argon.

Fiber optic sensor for angular position measurement: application for an electrical power-assisted steering system

To achieve a very effective automotive power steering system, we need two important data, the angular position of the wheel and the torque applied on the shaft by the driver of the car. We present a new accurate optical fiber angular position sensor connected to an automotive power steering column. In this new design, the sensor allows the measurement of the angular position of a car steering wheel over a large and adjustable range (± several turns of the wheel). The wheel rotation induces micro-bending in the transducer part of the optical fiber sensing system. This system operates as an amplitude modulation sensor based on mode coupling in the transducing fiber in the case when all the modes are equally excited. We study the sensor response both theoretically and experimentally with a multimode step index optical fiber [rf (fiber radius) = 300 μm; rc (core radius) = 50 μm; nc (core index) = 1,457; N.A. = 0, 22 and the wavelength is 632,8 nm at the ambient Temperature (20°C)]. We show that the sensitivity can be controlled as a function of the sensors length. We compare modeling and experimental validation and we conclude with a perspective on what could soon be an industrial sensor.